Oligomeric Proanthocyanidin Protects Retinal Ganglion Cells Against H₂O₂Induced Apoptosis In Vitro

Objectives: The death of retinal ganglion cells （RGCs） is a hallmark of many opticneurodegenerative diseases such as glaucoma and retinopathy. Oligomericproanthocyanidin （OPC）, the most abundant phenolic compounds in grape seeds andalso found in other plants, has many health beneficial effects including antioxidativeand neuroprotective actions. The purpose of the experiment was to test whether OPCmay protect RGCs against oxidative stress induced injury.Methods: Cells were treated with hydrogen peroxide with or without OPC. A seriesconcentration of OPC was tested. Cell viability of the RGC-5cell line was measuredwith a3-（4,5-Dimethylthiazol-2-yl）-2,5-diphenyl tetrazoliumbromide （MTT） assay.Hoechst33342assay, flow cytometry and Western blot were used to detect the apoptoticprocess and changes of related proteins. Then retinal explant culture was applied todetect the viability of RGCs in ganglion cell layer.Results: MTT assay showed that treating RGC-5cells with20μM OPC for7hourssignificantly decreased the H₂O₂induced death. Results of flow cytometry and Hoechststaining demonstrated that the death of RGC-5cells was mainly caused by cellapoptosis. We also found that OPC effectively inhibited the H₂O₂induced changes onapoptotic proteins such as Bax, Bcl-2and Caspase-3. Expression of Bax and Caspase-3were significantly decreased while Bcl-2was greatly increased in OPC treated groupwhen compared with the H₂O₂damaged group. Furthermore, in retinal explants culture,the surviving RGCs number in the H₂O₂group with OPC was significantly higher thanthe one in H₂O₂group without OPC. Conclusions: Our studies demonstrate that OPC can protect the oxidative stressinjured RGCs by reducing the apoptotic process, possibly by inhibiting themitochondrial pathway. This implies a role of OPC in the future clinical applications ofneuroprotection on RGCs and other neurons.